In recent years, there has been a demand to reduce the amount of CO2 released into the atmosphere in order to prevent global warming. As an effective means to reduce the amount of CO2, for example, there has been made a proposal to switch over to a solar system in which a photoelectrochemical cell such as silicon-based p-n junction solar cell is provided on the roof of house. However, there has been a problem that single crystal, polycrystal, or amorphous silicon used to fabricate such a silicon-based photoelectrochemical cell is high in cost because there is a need to set up high-temperature and high-vacuum conditions in its manufacturing process.
JP-W No. 7-500630 (Example A) discloses a photoelectrochemical cell which includes a photoelectric converter in which cis-bis(isothiocyanate)bis(2,2′-bipyridyl-4,4′-dicarboxylate)-ruthenium (II) represented by the formula (1) as an easy-to-produce photosensitizing dye is adsorbed on a thin film including titanium oxide fine particles.

However, there has been a problem that photoelectrochemical cells do not have sufficient photoelectric conversion efficiency at a long wavelength region above 700 nm.